The present invention relates generally to tape slitting machines of the type used for converting roll stock such as paper, plastic and cloth into smaller roll segments to provide roll strips or tapes. More particularly, the present invention is directed to a machine of the type in which the roll stock is rotated and a circular blade or cutting knife is presented radially toward the roll to penetrate the roll and to sever a segmental section therefrom. The process is repetitive so that the original roll is converted, stepwise, into a plurality of smaller rolls or roll segments.
A machine of the type in which the present invention finds utility is described in Witcraft et al U.S. Pat. No. 3,861,253, and the disclosure of that patent is incorporated herein by reference to the extent that it is not inconsistent herewith.
General procecures for cutting incremental sections from a larger roll to provide smaller segments are known in the art. Typically, the roll stock is rotated on a supporting mandrel and a freely revolving round blade or cutting knife carried on a shaft is presented radially toward to engage the roll, thereby to penetrate and cut and to sever a predetermined segmental width. When contact is made between the revolving roll of tape and the rotatable blade, the blade or knife itself is caused to rotate on its shaft. This blade rotation poses problems.
During such rotation, the blade is subject to "lateral run-out". That is, there is lateral shifting or displacement of the blade edge along a rotational axis of the revolving blade. As a result, the path of the cutting edge of the rotating blade is not limited to a single locus or plane. The blade edge oscillates laterally. Moreover, the roll to be cut does not have a "perfect" circle peripheral circumference. Nor does the cutting blade.
The overall effect of the "imperfect" physical structures described is that the edge of the cutting blade tends to engage the rotating roll stock, not in a single encircling path, but in a plurality of closely spaced but different cutting engagements, at least until the blade penetrates sufficiently into the roll stock to establish a stabilized condition in which the blade cuts through along a single radial path. The initial laterally displaced contacts cause nicking and multiple cutting. It will be appreciated that roll segments in which the marginal edge portions include multiple or secondary cuts cannot be unwound in use without break-off and other practical difficulties.
It is, therefore, a principal aim of the present invention to provide a simple yet highly effective apparatus and cutting technique whereby firm and positive single locus engagement is ensured between the cutting blade and the roll stock so as to obviate nicking, double cutting, and other deleterious effects of lateral shifting or run-out of the cutting blade during initiation of the cutting operation.